Spring Dates Research Articles

Effect of autumn cutting regime on developmental morphology and spring growth of perennial ryegrass

SummaryTwo field experiments were conducted at Aberystwyth on simulated swards of S. 23 perennial ryegrass which were cut one or more times between August and January. The further effect of cutting in early spring was also examined.The weight of harvestable herbage produced in spring was found to be much less from plots which had been cut frequently in autumn and winter, and was also reduced when the final cutting date was progressively delayed.The principal effect of later and more frequent cutting in autumn on developmental morphology was a dramatic reduction in the length of leaves produced subsequently. This effect persisted well into the spring period. Numbers of tillers and leaves were much less affected. Thus a greater bulk of herbage was present in spring on autumnrested swards. Production of new tillers in spring was, however, encouraged by greater levels of prior utilization, including cutting in March.Total herbage yields from the different defoliation systems up to and including different harvesting dates in spring were very similar, but contained a higher percentage of dead material when autumn growth had been allowed to accumulate for longer periods. Under these systems considerable numbers of leaves were formed but died without being harvested. Tiller survival at low temperatures was poorer in swards left undefoliated after the end of August.

Prediction by leaf analysis of nitrogen fertilizer required for winter wheat

AbstractIn 1966 and 1967, 12 experiments on winter wheat tested five rates of N applied in spring as NH4NO3. Leaf samples comprising all the above ground vegetation were taken on two dates in spring between 31 March and 18 May from a fixed area of crop grown without fertiliser N; the dry matter yield (DM, kg/ha) and N content (%) were determined. Between the two dates, DM increased and leaf N content decreased. From the response curves for N applied and grain yield, the optimum rate of fertilizer N required for maximum grain yield was obtained. The latter was used as a test of soil N availability and compared with the following values (i) content of N (%) in leaves at each sampling and its rate of decrease—no significant correlation, (ii) yield of leaf DM (kg/ha) at first sampling—no significant correlation, (iii) leaf DM yield at second sampling, significant (r= ‐0.678), and also rate of increase in DM (kg/ha per day, r= ‐0.711), (iv) leaf N offtake (kg/ha N) significant at first sampling (r= ‐0.607), second sampling (r= ‐0.744) and also rate of increase in N offtake (kg/ha N per day, r= ‐0.670). Crop growth in spring was related to N supply and it was shown that DM yield, leaf N offtake and their respective rates of increase could be used to assess the availability of N in the soil and to predict the amount of N fertilizer required in spring to obtain maximum grain yield.

Estimating minimum temperature and climatological freeze risk in hilly terrain

Differences between weather station and on-farm minimum temperatures in hilly terrain were related to general weather parameters, using stepwise multiple linear regression and correlation techniques. Opacity (cloud cover) and wind speed were the most significant parameters, explaining up to 79% of the variation in night-time temperature differences between base station and field sites 20–40 km away. Considering dew point depression, days since 0.25 cm rainfall, absolute minimum temperature, cloud base height, opacity as quadratic and an exponential relationship did not improve the regression estimates significantly. Standard error of estimates ranged from 0.8°C for sites on hilltops to 2.3°C for valley bottoms. In independent data tests using 19 cases, the average minimum temperature difference between the base station and a high risk site was estimated within 0.4°C of the measured value. Significance of the regression relationships increased proportionally with distance down the slopes. Base station-site minimum temperature differences on relatively clear calm nights averaged near 1°C on hilltops, 2° to 3°C midway down slopes and 5° to 6°C in the hollows. Regression equations developed from short-term temperature measurements at more than 50 sites were used to estimate daily site minimum temperatures for a 21-year period. Spring and fall freeze probabilities for critical temperatures of 32°, 30° and 28°F (0.0°, −1.1° and −2.2°C) were then calculated for each site using standard climatological techniques. Estimated average freeze dates in hollows were up to 34 days later in spring and 39 days earlier in fall than on hilltops. Average dates of spring and fall freeze occurrences were delayed and advanced respectively about 6 days for each degree (C) drop in critical temperature. In independent data tests the average spring and fall ground frost dates at the base station were estimated within 2 days of measured values, using similar techniques. Minimum temperatures measured by traverses on a clear, calm night were highly correlated with estimated frost dates ( R = 0.99).

PERFORMANCE OF SPRING WHEAT AND BARLEY CULTIVARS SOWN IN THE FALL AND SPRING IN NORTHERN ALBERTA

Two spring barley (Hordeum vulgare L. emend Lam.) and three spring wheat (Triticum aestivum L.) cultivars were grown over a 2-yr period at three locations in Alberta north of latitude 53°N, to compare the effect of fall and spring seeding on yield and maturity. The cultivars were Olli and Jubilee barley, and Park, Thatcher, and Pitic 62 wheat. The locations were Edmonton, Beaverlodge, and Fort Vermilion. With few exceptions, fall seeding resulted in loss of yield compared with spring seeding, and the fall-seeded materials were no earlier maturing than the comparable spring-seeded materials. For the cultivars and locations studied, fall seeding of spring barley and wheat cannot be recommended. Two spring seeding dates were also compared, the first being considerably earlier than typical commercial seeding at the same location. There were few significant differences in yield between the two spring dates, but the later date considerably delayed the maturity of all cultivars.

The effect of sowing date and season on growth and yield of oilseed rape (Brassica napus)

SummaryExperiments made between 1967 and 1970 tested the effects of sowing oilseed rape on different dates in autumn and spring. Much greater oil yields were obtained from autumn sowings, due to higher seed yields and oil content, but the effect varied considerably between experiments, varieties and seasons. Autumn-sown crops flowered in late April or early May, and by the time pods were developing rapidly in June the leaves had senesced almost completely. Spring-sown varieties followed a similar pattern but about a month later, and did not reach the same peak in pod growth.There was a major effect of sowing date, late-autumn sowings (after mid-September) giving lower yields than early-spring sowings. The best autumn sowings (early September) gave about 3 t/ha of seed, but late sowings less than half this; oil content also decreased with delay in sowing – from 45% to as low as 38%. Delayed sowing restricted growth, leaf area and pod production, and also had a slight effect on seed weight. Frost damage on flower buds appeared to be the cause of reduced yield from early sowing (August) in one experiment. In spring, the earliest sowing (late March) gave the best yields. Vigorous but late vegetative growth from the latest sowing (end of April) did not lead to high yields, possibly due to pest and disease effects.

THE ENSILAGE OF AUTUMN‐SOWN RYE

ABSTRACTAutumn‐sown rye was cut on five dates in spring and ensiled in laboratory silos. On two of the dates forage‐harvested material was ensiled in PVC silos (containing about 1 t of fresh crop) as well as in laboratory silos. Ensiling was carried out with and without the addition of formic acid or glucose solution. After 96 days in laboratory silos, rye cut before ear‐emergence and ensiled without additives gave silages of high pH value and high ammonia content. After ear‐emergence satisfactory silage was produced without an additive, but the addition of formic acid always resulted in silages having lower pH values and lower ammonia contents. The addition of glucose resulted in silages with only slightly lower pH values and ammonia contents which were closely similar to those made without addition. Silages made in PVC silos were all well preserved, as indicated by low contents of acetic and butyric acids, but the addition of formic acid resulted in pH values and ammonia contents lower than those found in other treatments.

Effects of Several Factors on Saltbush Establishment in California

Certain saltbush taxa can be established by direct seeding and may reduce fire hazards on fuel-breaks in California chaparral areas. Fourwing, allscale, and Gardner saltbushes were seeded at depths of 1/2 and 1 inch on four spring dates 2 to 4 weeks apart on noncalcareous soils at two test sites. A planting depth of 1/2 inch gave better results than 1 inch, and late spring when mean soil temperatures range between 60 and 65 F is apparently the best time for seeding if moisture is adequate. Fourwing saltbush produced the best stands and largest plants. The saltbush species and strains from sources doser to the planting site, or similar to it, or have the widest distributional range and tolerance to soil salts are most likely to be established by direct seeding and grow satisfactorily on neutral to slightly acid soil.

Effects of the Great Lakes' thermal influence on freeze-free dates in spring and fall as determined by Hopkins' bioclimatic law

In this paper, an attempt is made to show that Hopkins' (1938) bioclimatic law, in the form of an isophanic model, makes possible a quantitative declaration and examination of the thermal effects of the Great Lakes in advancing the beginning of the freeze-free season in the spring, and retarding its departure in the fall. For the first time, the number of days that the frost-free period is lengthened due primarily to the lakes' effect is determined. Similarly, the application of bioclimatic law has made possible a quantitative comparison of the degree of influence expressed by these water bodies on daily minimum temperatures at the start and end of the freeze-free season.

Burning Flint Hills Range

Burning has played an important role in the past management of Flint Hills range and still is common in that area. Old arguments against burning have been concerned with reduction of forage yield and water runoff (Elwell et al., 1941). It has been the purpose of this study to investigate the effects of burning bluestem range at various winter and spring dates on soil moisture from small plot studies and on range condition under stocking at a moderate rate with cattle. One of the first studies of range burning in the Flint Hills was that of Hensel (1923) who found no difference in forage production due to burning. Aldous (1934) reported more soil moisture in unburned than in burned plots and noted that time of burning may affect soil moisture. Further studies by Hanks and Anderson (1957) verified that soil in winter burned plots contained less moisture than soil in any other treatment. They were fortunate in having sampled before a 4.47-inch rain which came in an intense storm in late September. Subsequent sampling showed that unburned plots retained 83% of that pre-